1. Field of the Invention
This invention relates generally to the preparation of thermosetting oligomers, some of which cure into polymeric products having conjugated molecular structures. More particularly, the invention relates to the preparation of acetylene-substituted Schiff's bases and the polymeric products derived therefrom.
2. Prior Art
Extensive research has been conducted on the part of Applicant herein and others to develop thermosetting resins or oligomers suitable for use in the preparation of high temperature composites and adhesives. A principal goal of this research has been to develop thermosetting resins or prepolymers which cure through addition reactions to form thermally stable materials with little or no voids.
Examples of this prior art work are shown in the publications of Fred E. Arnold and Robert F. Kovar entitled "Polyphenylquinoxalines With Terminal Acetylene Groups," published (a preprint for the 8th National Society for the Advancement of Materials and Process Engineering technical conference in Seattle, Washington), Oct. 12-14, 1976; P. M. Hergenrather entitled "Crosslinking High Temperature Polymers, Particularly Polyphenylquinoxalines," published as a preprint for the 172nd meeting of the American Chemical Society in San Francisco, California, in August-September of 1976 (Vol. 36, No. 2); and Frederick L. Hedberg et al entitled "Benzil End-Capped Acetylene Terminated Phenylquinoxalines," published in the American Chemical Society Polymer preprints, Vol. 18, No. 1, in March of 1977, and in U.S. Pat. Nos. 3,845,018 and 3,879,349 issued to Norman Bilow et al on Oct. 29, 1974 and Apr. 22, 1975, respectively as well as U.S. Pat. 3,897,395, issued to Gaetano F. D'Alelio.
All of the oligomers described in the above-stated prior art need to be polymerized at temperatures of 200.degree. C. or above, none yield viscous tacky intermediate state polymer melts, and none of them are fully conjugated compounds which can be polymerized into conjugated resins.
Oligomers susceptible to being processed as viscous tacky intermediate state polymers and with the ability to cure at temperatures below 200.degree. C. are desired to facilitate the formation of composites with minimal processing difficulties. Conjugated materials such as these oligomers are desired for use as light weight electrical conductor and/or semiconductor applications.
Applicant knows of no polymeric compounds susceptible to the formation of thermally stable high temperature composites that are easily processed, cure at relatively low temperatures (as low as 150.degree. C.) and function as either conductors or semiconductors.
It is therefore an objective of this invention to provide a new class of homopolymerizable prepolymers which cure without gas evolution.
A second objective of this invention is to provide fully conjugated compounds which can be homopolymerized into completely conjugated polymers.
A third objective of this invention is to provide thermosetting prepolymers which cure at temperatures as low as 150.degree.-160.degree. C.
A fourth objective of this invention is to provide acetylene-substituted prepolymers that can be caused to polymerize into viscous tacky products prior to undergoing complete cures.